Taking all the length issues into consideration, If you want to keep the truck tandem axle, its very easy to do, and your can extend the bed even further than 11foot.
If you single the rear, then some design considerations come into play.
Single long, and your turning radius is the same as staying tandem.
Single short- the truck doesn't look proportional in the deck length, axle spacing etc
Single to a "Mid" position- drop the front axle and roll the rear axle forward to where the center of the tandem position was. This looks the best but you are still limited some in your length.
The other issue is that while moving the hitch aft of the rear axle is nice for tracking and backing into tight spots, there is a limit to how far aft you can go. 6ft has been determined to be about the max distance the hitch can be placed behind the rear axle without issue. More than that and you start getting travel trailer type problems like sway control.